In a gas turbine, such as is known, for example, from U.S. Pat. No. 6,312,219 B1, one or more gas turbine stages drive one or more compressor stages and/or fans via one or more shafts. In one or more of the gas turbine stages, a stator vane array is provided downstream of a rotor blade array to vary the velocity of the gas flow.
If, in the event of a shaft breakage, the compressor load is abruptly removed, the gas turbine stage(s) may overspeed, which is not desired. Such overspeeding can be reduced or prevented in that the fast rotating rotor blade array of a gas turbine stage is axially displaced toward an adjacent stator vane array, rotates into contact therewith, and is braked by it.
To this end, the rotor blade array must overcome a minimum axial gap between the rotor blade array and the stator vane array. This gap is intended to prevent, to the extent possible, rubbing contact during normal operation, which may occur due to axial tolerances resulting from thermal effects, manufacture, assembly and/or dynamic effects.
In U.S. Pat. No. 6,312,219 B1, this minimum axial gap is formed in a radially inner region between a blade root of the rotor blade array and a shroud of the stator vane array.